1. Field of the Invention
The present invention relates to a peak level detection circuit for detecting the peak level of a pulse train of alternative mark inversion (AMI) signals etc.
A peak level detection circuit must be able to quickly follow and detect the peak level of an input pulse train even when the peak level changes along with time.
2. Description of the Related Art
In a data transmission and reception system, when transmitting data comprised of the logic "1" and "0" from one data terminal equipment to another data terminal equipment, the other data terminal equipment discriminates the "1" or "0" of the received data in accordance with whether the peak level of the pulses of the received input pulse train is higher or lower than a predetermined threshold level. In this case, the peak level of the pulses varies over time, so it is necessary to make the above-mentioned threshold level higher or lower in accordance with the variation in the high or low changes of the peak level.
Therefore, the peak level of the pulses of the input pulse train is continually monitored so as to set a threshold level conforming with the peak level (for example, 1/2of the peak level). For this, a peak level detection circuit is required for detecting the peak level of the pulses of the input pulse train.
In the past, this peak level detection circuit, as will be explained in detail later, received one series of input pulse trains at the data terminal equipment then received another series of input pulse trains after a while. In that case, there was a problem when the peak level of the pulses of the latter input pulse trains was lower than the peak level of the pulses of the former input pulse trains. The problem was that the peak level detection circuit would end up detecting a mistaken peak level in the considerably long time from when the latter pulse trains began to be received. Therefore, data error would occur during that time.